The present invention is generally in the field of assessment of condition of batteries and, more particularly, systems for sensing current to and from a battery over a period of time and for sensing temperature at which the current occurs.
In some applications of batteries, such as automotive and aircraft power systems, a battery may provide continuous power at a low rate for some control systems. The same battery may also provide power at a high current rate for limited times for tasks such as engine starting. The battery may be in place within a vehicle for an extended time, during which time the vehicle may be exposed to varying environmental temperature. Recharging batteries may occur at low, so-called trickle rates and also at high current rates.
A battery may have only a limited useful lifetime. Its useful lifetime may be limited by factors such as times and rates of discharge, times and rates of re-charge and amounts of time that a battery may be exposed to various temperatures. In particular, exposing a battery to low temperature may have the effect of shortening its useful lifetime.
In many battery applications, battery health systems or prognosis systems may be employed to predict or determine if a battery may be capable of performing its high current tasks, such as engine starting, when needed. These prognosis systems may continuously collect data relating to rates of current discharge and/or re-charge and time periods over which these current rates occurred. Additionally, a typical battery prognostic system may continually collect data relating to times that a battery is exposed to any particular temperature. Such data may then be processed to provide a prediction of future useful life of the battery.
In the past, battery prognosis systems were employed only in specialized vehicles such as high-risk military vehicles. As automotive and aircraft electrical system designs have evolved, battery prognosis systems are often used on more conventional vehicles such as civilian automobiles. In this regard, battery prognosis systems are being employed in ever increasing volumes. Consequently, manufacturing cost for such systems becomes an increasingly important consideration.
Prior-art vehicular-battery prognosis systems may employ a current sensor and a separate temperature sensor. Use of two different sensors contributes to high cost and complexity of such prognosis systems. There are known techniques for measuring current and temperature with a single sensor (e.g. US Patent Application Publication 2005/0077890, R. Rannow et al). These known techniques, while combining two sensing functions in a single device, are nevertheless complex and expensive. As a result, these single sensor current/temperature measurement systems have not been employed in prior-art vehicular battery prognosis systems.
Additionally, prior-art battery prognosis systems have employed sensors which are separate from processors and controls. In a typical prior-art system, a printed wiring board (PWB) may support processing and control functions while sensors are provided as devices separate from the PWB.
As can be seen, there is a need to provide a battery prognosis system that may be produced at a low cost. Additionally there is a need to provide a system in which current sensing and temperature sensing may be combined in a single low cost device. Still further there is a need to provide such a system in which a sensor is integrated into a PWB on which processing and control is performed.